The 68-year-old woman was pushing a walker when the man came up behind her and grabbed her around the throat as she struggled to understand what was happening, police said.

“When you watch the video, you can actually read the [suspect's] mind as he sizes up his victim and waits for witnesses to walk by,” Lt. Paul Vernon, commanding officer of the Central detective division, said in a statement.

A man in a nearby business interrupted the robbery and the suspect ran away with a gold chain and jade pendant, valued at $100, police said. Detectives were reviewing other video taken at the scene for other footage of the suspect.

Police are asking anyone with information to call detectives at (213) 972-1251 or leave a message on "webtips" at www.LAPDOnline.org.